Uninterruptible power supply with total isolation

Abstract

An uninterruptible power supply includes an isolation transformer having dual primary windings. The secondary winding generates an output voltage based on the magnetic field generated in one of the dual primary windings. A first primary winding is coupled to an inverter circuit that receives an alternating current input voltage and applies a clean and filter alternating current to the first primary winding. A second primary winding is coupled to a bypass circuit that applies a bypass voltage when the inverter circuit is in a failure state. The power supply also includes a compensation circuit to maintain the output voltage at a desired level.

1. An uninterruptible power supply comprising:
 an isolation transformer having dual primary windings and a secondary winding to supply an output voltage; 
 a first winding of the dual primary windings coupled to an inverter circuit that receives an alternating current input voltage; and 
 a second winding of the dual primary windings coupled to a bypass circuit that receives a bypass voltage, 
 wherein voltage is applied to the second winding upon failure of the inverter circuit to generate the output voltage without interruption, 
 wherein the inverter circuit includes a compensation circuit to provide a compensation voltage that maintains the output voltage at an approximately constant level by using feedback from a load current into the first winding of the duel primary windings of the isolation transformer, 
 wherein the compensation circuit includes a voltage compensator to generate the compensation voltage based on the load current into the first winding of the duel primary windings of the isolation transformer, 
 wherein said compensation circuit includes a current transformer, 
 wherein said current transformer is directly connected to the output input of the first winding and is also directly connected to the voltage compensator, wherein the voltage compensator is connected to an inverter located within the inverter circuit. 
 
     
     
       2. The uninterruptible power supply of  claim 1 , wherein the inverter circuit includes a filter circuit coupled to the first winding. 
     
     
       3. The uninterruptible power supply of  claim 1 , wherein a number of windings in the secondary winding differs from a number of windings in the first or the second winding. 
     
     
       4. The uninterruptible power supply of  claim 1 , wherein the bypass voltage differs from the output voltage. 
     
     
       5. The uninterruptible power supply of  claim 1 , wherein said isolation transformer is a 3-phase isolation transformer. 
     
     
       6. The uninterruptible power supply of  claim 5 , wherein said duel primary windings have a delta configuration and said secondary windings have a Y configuration. 
     
     
       7. The uninterruptible power supply of  claim 1 , wherein said feedback used by said voltage compensation circuit comes only from said current transformer. 
     
     
       8. An uninterruptible power supply comprising:
 an isolation transformer, wherein the isolation transformer includes a first primary winding coupled to an inverter circuit that receives an alternating current input voltage, a second winding coupled to a bypass circuit that receives a bypass voltage, and a secondary winding; 
 the inverter circuit includes a diode to generate a direct current voltage and an inverter to convert the direct current voltage to an alternating current voltage that receives a compensation voltage before applied to the first primary winding, wherein the alternating current voltage is cleaner than the alternating current input voltage; 
 a compensation circuit to detect a load current to the first primary winding and to generate the compensation voltage based on the load current; and 
 an output coupled to the secondary winding to provide an output voltage corresponding to the bypass voltage or the alternating current voltage, 
 wherein said compensation circuit includes a current transformer, 
 wherein said current transformer is directly connected to the output of the first winding and is also directly connected to the voltage compensator, 
 wherein the voltage compensator is connected to an inverter located within the inverter circuit. 
 
     
     
       9. The uninterruptible power supply of  claim 8 , wherein the bypass voltage is approximately the same as the output voltage. 
     
     
       10. The uninterruptible power supply of  claim 8 , wherein the alternating current voltage and the compensation voltage are approximately the same as the output voltage. 
     
     
       11. The uninterruptible power supply of  claim 8 , wherein the isolation transformer only uses the first primary winding or the second primary winding to generate the output voltage. 
     
     
       12. An isolation transformer comprising:
 a first primary winding coupled to an inverter circuit, wherein the inverter circuit provides an alternating current voltage to the first primary winding based on an alternating current input voltage; 
 a second primary winding coupled to a bypass circuit to provide a bypass voltage; and 
 a secondary winding to generate an output voltage without interruption according to the first primary winding or the second primary winding, wherein the second primary winding is used upon failure of the first primary winding, 
 wherein the inverter circuit includes a compensation circuit to provide a compensation voltage that maintains the output voltage at an approximately constant level by using feedback from a load current into the first winding of the primary windings of the isolation transformer, 
 wherein the compensation circuit includes a voltage compensator to generate the compensation voltage based on the load current into the first winding of the primary windings of the isolation transformer, 
 wherein said compensation circuit includes a current transformer, 
 wherein said current transformer is directly connected to the output of the first winding and is also directly connected to the voltage compensator, 
 wherein the voltage compensator is connected to an inverter located within the inverter circuit. 
 
     
     
       13. The isolation transformer of  claim 12 , wherein the output voltage is approximately equal to the alternating current voltage. 
     
     
       14. The isolation transformer of  claim 12 , wherein the output voltage is stepped up or stepped down from the alternating current voltage or the bypass voltage. 
     
     
       15. A method for supplying power without interruption, the method comprising:
 determining whether an inverter circuit is in a failure state; 
 applying an alternating current voltage using the inverter circuit to a first primary winding of an isolation transformer if the inverter circuit is not in the failure state; 
 applying a bypass voltage to a second primary winding of the isolation transformer if the inverter circuit is in the failure state; 
 generating an output voltage using a secondary winding of the isolation transformer based on the alternating current voltage or the bypass voltage, 
 detecting a load current to the first primary winding, adjusting the alternating current voltage applied to the first primary winding with a compensation voltage, 
 wherein the compensation voltage is based on feedback from the detected load current to the first primary winding, 
 wherein said compensation circuit includes a current transformer, 
 wherein said current transformer is directly connected to the output of the first winding and is also directly connected to the voltage compensator, 
 wherein the voltage compensator is connected to an inverter located within the inverter circuit. 
 
     
     
       16. The method of  claim 15 , further comprising filtering the alternating current voltage. 
     
     
       17. The method of  claim 15 , further comprising receiving an alternating current input voltage at the inverter circuit.